Wet-gas flowmeter

Abstract

Methods and apparatus determine phase fractions for phases within a fluid mixture flow under a wide range of flow conditions including wet-gas flow. Appropriate flow algorithms can utilize this phase fraction information with a total flow rate of the mixture to find individual flow rates for phases, such as oil, water, and gas or gas and liquid, which can represent a combination of oil and water phases. For some embodiments, a multiphase flowmeter includes an array of spatially distributed pressure sensors configured to determine a velocity of the mixture flow and hence the total flow rate, which is applied with information from a differential pressure meter to calculate the bulk density of the fluid mixture. Further, additional speed of sound information or a water-in-liquid ratio as may be determined by spectral analysis can enable differentiation between the oil and water phases.

1. An apparatus for measuring flow of a fluid mixture in a conduit, comprising:
 a pressure sensor array based meter comprising an array of sensors that detect pressure variations traveling with the fluid mixture; and 
 a water-in-liquid ratio meter configured to perform an infrared optical based spectroscopy analysis of the fluid mixture. 
 
     
     
       2. The apparatus of  claim 1 , wherein the spectroscopy analysis includes attenuation measurements of wavelength bands absorbed by water compared to attenuation of wavelength bands substantially transmitted through water. 
     
     
       3. The apparatus of  claim 1 , wherein the pressure sensor array based meter further detects acoustic pressure variations traveling at the speed of sound in the fluid mixture. 
     
     
       4. The apparatus of  claim 1 , wherein at least one of the sensors comprises a coil of optical fiber wrapped around the conduit. 
     
     
       5. An apparatus for measuring flow of a fluid mixture in a conduit, comprising:
 a differential pressure based meter configured to detect a differential pressure across a fluid flow pressure change inducing section along the conduit; and 
 a water-in-liquid ratio meter configured to perform an infrared optical based spectroscopy analysis of the fluid mixture. 
 
     
     
       6. The apparatus of  claim 5 , wherein the spectroscopy analysis includes attenuation measurements of wavelength bands absorbed by water compared to attenuation of wavelength bands substantially transmitted through water. 
     
     
       7. The apparatus of  claim 5 , wherein the fluid flow pressure change inducing section comprises a flow nozzle. 
     
     
       8. The apparatus of  claim 5 , wherein the fluid flow pressure change inducing section comprises a flow nozzle formed by the conduit. 
     
     
       9. The apparatus of  claim 5 , wherein the fluid flow pressure change inducing section comprises an orifice plate or a V-cone. 
     
     
       10. The apparatus of  claim 5 , wherein an inner diameter of the conduit converges to a throat section in the fluid flow pressure change inducing section. 
     
     
       11. The apparatus of  claim 10 , wherein the water-in-liquid ratio meter is disposed at the throat section of the fluid flow pressure change inducing section. 
     
     
       12. The apparatus of  claim 5 , wherein the water-in-liquid ratio meter is disposed downstream of the differential pressure based meter. 
     
     
       13. An apparatus for measuring flow of a fluid mixture in a conduit, comprising:
 at least one of a flow velocity meter configured to sense along the conduit pressure variations traveling with the fluid mixture and a differential pressure based meter configured to sense a differential pressure across a fluid flow pressure change inducing section along the conduit; 
 a water-in-liquid ratio meter configured to perform an infrared optical based spectroscopy analysis of the fluid mixture; and 
 a processor configured with logic to determine a total flow rate from the at least one of the flow velocity meter and the differential pressure based meter, to determine one or more phase fractions based on the infrared optical based spectroscopy analysis, and to calculate one or more phase flow rates based on the phase fractions and the total flow rate. 
 
     
     
       14. The apparatus of  claim 13 , wherein the phase fractions comprise individual oil, gas, and water fractions and the phase flow rates comprise individual oil, gas, and water flow rates. 
     
     
       15. The apparatus of  claim 13 , wherein the fluid flow pressure change inducing section comprises a flow nozzle. 
     
     
       16. The apparatus of  claim 13 , wherein the fluid flow pressure change inducing section comprises a flow nozzle formed by the conduit. 
     
     
       17. The apparatus of  claim 13 , wherein the fluid flow pressure change inducing section comprises a Venturi. 
     
     
       18. The apparatus of  claim 13 , wherein an inner diameter of the conduit diverges in the fluid flow pressure change inducing section. 
     
     
       19. The apparatus of  claim 13 , wherein the flow velocity meter comprises an array of pressure sensing elements. 
     
     
       20. The apparatus of  claim 19 , wherein at least one of the pressure sensing elements comprises a coil of optical fiber wrapped around the conduit.